An assessment of the utility of an acoustic Doppler current profiler for biomass estimation

first_imgAcoustic Dopplerd current profilers (ADCPs) are being used increasingly to derive estimates of zooplankton and micronekton abundance. The absence of a practical means for users to perform ADCP calibration, however, makes the quantitative value of this approach questionable. In an attemptto evaluate ADCP-derived volume backscattering strength (Sv) data, and hence to assess the utility of such measurements for biomass estimation, a regularly calibrated Simrad EK500 scientific echo-sounder (operating at 38, 120 and 200 kHz) and an RDI narrow-band ADCP (153.6 kHz) were similarly configured and run in synchrony on a transect in the Southern Ocean. Data were collected by both instruments from congruent depth (4 m) and time (2 min) bins in order to allow direct comparison of numerous discrete values without the need for further signal averaging. Echoes were recorded from the Antarctic krill, Euphausia superba,in deep-ocean and on-shelf locations during day and night. ADCP-derived volume back scattering strength data from shallow, evenly distributed krill targets were well correlated with equivalent data from the EK500 (r2>0.98), and the offsets between instruments conformed to those predicted for their respective operating frequencies by a theoretical model of sound scattering by krill (H0: Sv 153.6 kHz=Sv 120 kHz+2.3 dB, ). Data from deeper, more irregularly distributed targets differed significantly (P<0.001). We conclude that under some ideal, but probably rare, circumstances data from the ADCP can be used to derive biomass estimates. The numerous uncertainties surrounding ADCP calibration and the current practical impossibility for users to monitor system performance should, however, preclude these instruments from being used as a matter of course to determine abundance estimates, a task that we believe should remain firmly within the domain of a well calibrated scientific echo sounder.last_img read more

Simultaneous measurements of the O2(¹Δ) and O2(¹Σ) Airglows and ozone in the daytime mesosphere

first_imgWe report simultaneous measurements of the O2(¹Δ) and O2(¹Σ) airglow volume emission rate profiles in the daytime mesosphere. We use these measurements to derive ozone concentrations separately from each airglow. The measurements were made as part of the Mesosphere‐Thermosphere Emissions for Ozone Remote Sensing (METEORS) sounding rocket project launched from White Sands Missile Range, New Mexico. These data offer the opportunity to assess the consistency of ozone profiles derived from measurements of the oxygen airglows and thus provide a fundamental test of our understanding of dayglow physics and solar energy deposition. In both airglow‐derived profiles the ozone decreases with altitude throughout the middle mesosphere and a pronounced secondary maximum exists near 90 km. The derived ozone profiles are in agreement to within measurement uncertainty. This agreement confirms that the major processes responsible for the generation of mesospheric oxygen dayglow are well understood via measurement.last_img read more

Equilibrium temperature of water-ice aerosols in the high-latitude summer mesosphere

first_imgPrevious models of the equilibrium temperature and existence regions of mesospheric aerosols have shown significant radiative heating of the aerosols and, consequently, a substantially reduced existence region. We have developed an iterative model that extends this previous work by incorporating a complete collisional energy transfer algorithm, including the effects of vertical winds and particle fall velocity, that is appropriate for the free molecular flow conditions found in the mesosphere. We have also updated the ice refractive index used in the model and accounted for the dependence of the radiative heating and collisional cooling terms on particle tempe;ature. Finally, a radiation model has been used to calculate the solar, terrestrial and atmospheric radiative inputs including the effects of multiple scattering and atmospheric absorption. As with the previous models, the particle temperature is calculated under steady-state conditions, assuming the background gas temperature remains constant and the aerosol does not change size, state or altitude. Under these conditions, the largest differences from previous models occur as a result of the updated ice index of refraction, particularly in the visible, which produces significantly less aerosol heating. These temperatures are combined with the observed properties of mesospheric aerosols to place limits on the water vapour mixing ratio, vertical-wind speeds, and maximum particle sizes. It is found that H2O mixing ratios of 10 ppmv and vertical winds of order 0.02 m s(-1) are consistent with observed particle distributions, and these lead to a radiative limit on the maximum particle radius of 250 nm.last_img read more

Synoptic analysis of the Pacific-North American teleconnection pattern

first_imgIn this study, we use various diagnostic techniques to investigate the synoptic evolution of the Pacific–North American teleconnection pattern (PNA). National Center for Environment Prediction/National Center for Atmospheric Research reanalysis data are used. These data cover the years 1948–2008 for the months of November–March. It is found that the positive PNA is initiated by enhanced convection over the western tropical Pacific and weakened convection over the tropical Indian Ocean. The excitation of the negative PNA exhibits opposite features. For both phases, the response to tropical convection excites a small-amplitude PNA about 8–12 days prior to the pattern attaining its maximum amplitude. This is followed by slow, steady growth for about 5 days, after which driving by synoptic scale waves, via their eddy vorticity flux, together with stationary eddy advection lead to much more rapid growth and the establishment of the full PNA. For the positive PNA, the synoptic scale waves propagate eastward into the midlatitude northeastern Pacific, where they are observed to undergo cyclonic wave breaking. For the negative PNA, the synoptic scale waves first amplify over the midlatitude northeastern Pacific and then propagate equatorward into the Subtropics where they undergo anticyclonic wave breaking. Once established, for both phases, the PNA appears to be maintained through a positive feedback that involves a succession of wave breakings. These results suggest that preconditioning may play an important role in the formation of the PNA. For the positive PNA, in its early development, the strengthening and eastward extension of the subtropical jet result in an increase in the cyclonic shear and a decrease in the meridional potential vorticity gradient, features that are known to favour cyclonic wave breaking. For the negative PNA, opposite changes were observed for the background flow, which favour equatorward wave propagation and anticyclonic wave breaking. The role of optimal growth is also discussed. Our results also suggest that the PNA is potentially predictable 1–2 weeks in advance. Copyright © 2011 Royal Meteorological Societylast_img read more

Flow at ice-divide triple junctions: 1. Three-dimensional full-Stokes modeling

first_imgIce domes are either axisymmetric, high points along ridges, or ridge triple junctions. We model time-dependent isothermal flow near triple junctions, solving the full set of mechanical equations with a nonlinear power law rheology. Forcing is applied through the boundary conditions, which affect flow patterns at outlets. Where such forcing is purely axisymmetric, an axisymmetric dome is formed. If a threefold symmetry in the forcing is applied, the axisymmetric dome breaks up into three ridges subtending angles of 120 degrees. Sets of experiments where the forcing was not exactly threefold symmetric by angle or by amplitude caused the triple junction to migrate to a new steady state. Here, in steady state, the ridges join the triple junction at nearly 120 degrees, but one ridge curves to satisfy the boundary forcing. The slope pattern in the immediate dome vicinity depends only on a dimensionless parameter, which is a function of the ice consistency, the accumulation, and the rheological power law index. Attempts to replicate the topography around Summit, Greenland, obtained a good fit with n = 3. At a triple junction the dome is really distinct from the surrounding ridges, contrary to the highest point of a single ridge divide. As a consequence, the Raymond effect is at its strongest at the dome and weakens considerably over one ice thickness as one moves away from the flow center. Along the ridges leaving the dome, the Raymond effect is still present and decreases with the ratio of the flow across and along the ridge. In the vicinity of the dome, horizontal strain rates vary strongly from uniaxial to biaxial. Large-scale effects, represented in our model as fluxes at boundaries, seem to be the primary controls on dome position and shape.last_img read more

Framework for mapping key areas for marine megafauna to inform Marine Spatial Planning: the Falkland Islands case study

first_imgMarine Spatial Planning (MSP) is becoming a key management approach throughout the world. The process includes the mapping of how humans and wildlife use the marine environment to inform the development of management measures. An integrated multi-species approach to identifying key areas is important for MSP because it allows managers a global representation of an area, enabling them to see where management can have the most impact for biodiversity protection. However, multi-species analysis remains challenging. This paper presents a methodological framework for mapping key areas for marine megafauna (seabirds, pinnipeds, cetaceans) by incorporating different data types across multiple species. The framework includes analyses of tracking data and observation survey data, applying analytical steps according to the type of data available during each year quarter for each species. It produces core-use area layers at the species level, then combines these layers to create megafauna core-use area layers. The framework was applied in the Falkland Islands. The study gathered over 750,000 tracking and at-sea observation locations covering an equivalent of 5495 data days between 1998 and 2015 for 36 species. The framework provides a step-by-step implementation protocol, replicable across geographic scales and transferable to multiple taxa. R scripts are provided. Common repositories, such as the Birdlife International Tracking Database, are invaluable tools, providing a secure platform for storing and accessing spatial data to apply the methodological framework. This provides managers with data necessary to enhance MSP efforts and marine conservation worldwide.last_img read more

Acute oil exposure reduces physiological process rates in Arctic phyto- and zooplankton

first_imgArctic shipping and oil exploration are expected to increase, as sea ice extent is reduced. This enhances the risk for accidental oil spills throughout the Arctic, which emphasises the need to quantify potential consequences to the marine ecosystem and to evaluate risk and choose appropriate remediation methods. This study investigated the sensitivity of Arctic marine plankton to the water accommodated fraction (WAF) of heavy fuel oil. Arctic marine phytoplankton and copepods (Calanus finmarchicus) were exposed to three WAF concentrations corresponding to total hydrocarbon contents of 0.07 mg l−1, 0.28 mg l−1 and 0.55 mg l−1. Additionally, the potential phototoxic effects of exposing the WAF to sunlight, including the UV spectrum, were tested. The study determined sub-lethal effects of WAF exposure on rates of key ecosystem processes: primary production of phytoplankton and grazing (faecal pellet production) of copepods. Both phytoplankton and copepods responded negatively to WAF exposure. Biomass specific primary production was reduced by 6, 52 and 73% and faecal pellet production by 18, 51 and 86% with increasing WAF concentrations compared to controls. The phototoxic effect reduced primary production in the two highest WAF concentration treatments by 71 and 91%, respectively. This experiment contributes to the limited knowledge of acute sub-lethal effects of potential oil spills to the Arctic pelagic food web.last_img read more

SUU Men’s Basketball Visits Idaho State Thursday

first_imgJanuary 7, 2020 /Sports News – Local SUU Men’s Basketball Visits Idaho State Thursday Tags: Idaho State basketball/SUU Basketball Written by FacebookTwitterLinkedInEmailPOCATELLO, Idaho-Thursday evening, Southern Utah men’s basketball (9-5, 2-1 in Big Sky Conference play) visits Reed Gym to battle the Idaho State Bengals (5-7, 2-1 in Big Sky).In his fourth season at SUU, head coach Todd Simon (45-68, .398) has the Thunderbirds in third place in the Big Sky after a 59-53 win over Montana State Saturday at the America First Event Center.SUU scores 74.8 points per game, which ranks the Thunderbirds 112th in scoring offense.Junior guard John Knight III (13.1 points per game) leads SUU in scoring and is tied for a team-best 32 assists with redshirt senior guard/forward Cameron Oluyitan (12.6 points, 5.1 rebounds per game).Redshirt senior forward Dwayne Morgan (11 points per game) also scores in double figures on-average for the Thunderbirds this season.Sophomore guard Harrison Butler leads the squad in rebounds (7.9 per game) and is tied for the team lead in blocked shots with sophomore forward Maizen Fausett (11 blocked shots per contest).The Thunderbirds out-rebound opponents 40.1-31.7 per game as their +8.4 rebound margin per game ranks them 17th nationally.SUU surrenders 63.9 points per game, ranking the Thunderbirds 67th nationally in scoring defense.The Bengals are coached by first-year head coach Ryan Looney (5-7, .417) and are coming off of a 68-49 loss to Sacramento State last Saturday.Idaho State scores 68.5 points per game as the Bengals are tied for 253rd nationally in scoring offense with UNLV.Junior guard Tarik Cool leads Idaho State in scoring (14.6 points per game), steals (15) and assists (43).Senior forward, Australian national Chier Maker (12.2 points, 5.3 rebounds per game) and senior guard Jared Stutzman (10.2 points per game) also score in double figures on-average for the Bengals.Senior forward Chidi Udengwu leads Idaho State in rebounding (5.9 boards per game) and junior forward Malik Porter has a team-best 11 blocked shots for the Bengals.The Thunderbirds lead the Bengals 19-12 all-time and have won four of their last five games against Idaho State in the series. Brad Jameslast_img read more

Prep Sports Roundup: 10/1

first_img Tags: Roundup October 1, 2020 /Sports News – Local Prep Sports Roundup: 10/1 FacebookTwitterLinkedInEmailVolleyballRegion 14LINDON, Utah-The Juab Wasps bested Maeser Prep 3-0 in Region 14 volleyball action Thursday. The Wasps prevailed 25-10, 25-11 and 25-18 to earn the win in straight sets.MT. PLEASANT, Utah-The Union Cougars gashed North Sanpete 3-0 Thursday in Region 14 volleyball action.Region 16COALVILLE, Utah-The North Summit Braves routed North Sevier 3-0 Thursday in Region 16 volleyball action. The Braves prevailed 25-10, 25-12 and 25-7 to down the Wolves in straight sets.ALTAMONT, Utah-The Gunnison Valley Bulldogs waxed Altamont 3-0 in Region 16 volleyball action Thursday. The Bulldogs prevailed 25-15, 25-14 and 25-14 to overpower the Longhorns in straight sets.Region 18FILLMORE, Utah-The Millard Eagles surged past Beaver 3-1 Thursday in Region 18 volleyball action. The Eagles waxed the Beavers 22-25, 25-17, 25-20 and 26-24 in the clincher.Non-RegionMT. PLEASANT, Utah-The Wasatch Academy Tigers dismantled Utah Military-Camp Williams 3-0 Thursday in non-region volleyball action. The Tigers stymied the Marauders 25-13, 25-5 and 25-11 to post the straight sets victory.GREEN RIVER, Utah-The Wayne Badgers sank the Green River Pirates 3-1 in non-region volleyball action Thursday. The Badgers prevailed 20-25, 31-29, 25-17 and 25-16 in the clincher to pull out the victory.PANGUITCH, Utah-Kanab surged past Panguich 3-1 Thursday in non-region volleyball action. Kanab downed the Bobcats, 24-26, 25-18, 26-24 and 33-31 to seal the deal.FREDONIA, Arizona-The Escalante Moquis earned a straight set sweep over Fredonia 3-0 Thursday in non-region volleyball action.Girls Soccer2-A SouthPAROWAN, Utah-Laci Sissener amassed a hat trick as the Parowan Rams clobbered Beaver 11-0 in 2-A South girls soccer action Thursday. Brooklyn Hulet and Lina Biasi had 2 goals apiece for the Rams in the win. Karlee Wood, Maddee Mathews, Madee Leydsman and McKenna Murphy also added goals in the win for Parowan.Region 12RICHFIELD, Utah-Nora Foster’s hat trick led the way as the Richfield Wildcats hammered South Sevier 12-0 Thursday to win the Region 12 title. Holly Torgersen added 2 more goals in victory for the Wildcats. Alexis Kling, Brittan Tait, Kate Robinson and Melissa Crane also scored in the win for the Wildcats. Megan Terry earned the shutout for Richfield.Region 14NEPHI, Utah-Marissa Hall posted a pair of goals and the Juab Wasps blanked American Leadership 5-0 in Region 14 girls soccer action Thursday. CheyAnn Lewis, Josephine Kay and Melea Ludlow also scored in victory for Juab. Jacie Bergstrom posted the shutout for the Wasps.MANTI, Utah-Allie Bridges scored twice and the Manti Templars stymied Maeser Prep 6-0 Thursday in Region 14 girls soccer action. Alivya Osborn, Ally Squire, Elsey Olson and Jayci Jolley also scored in victory for Manti. Katie Larsen earned the win in the net for the Templars.MT. PLEASANT, Utah-The Union Cougars blanked North Sanpete 1-0 in Region 14 girls soccer action Thursday. Brad James Written bylast_img read more

Harding scores 17 points, BYU cruises past Utah 82-64

first_img Written by FacebookTwitterLinkedInEmailPROVO, Utah (AP) — Connor Harding scored 17 points, Richard Harward didn’t miss a shot and had a career-high 15 points, and BYU beat rival Utah 82-64.BYU (6-2) avenged last season’s 102-95 overtime road loss to the Utes (2-1).Harding was 6 of 8 and Harward 7-of-7 shooting from the floor. BYU’s leading scorer Alex Barcello had just five points but a career-best eight assists.Alfonso Plummer made four 3-pointers and scored 19 points to lead Utah.BYU used a 15-3 run that included Johnson’s fourth 3-pointer to extend its lead to 71-51 with 5:37 remaining. December 12, 2020 /Sports News – Local Harding scores 17 points, BYU cruises past Utah 82-64 Tags: BYU Cougars Basketball/Connor Harding/Utah Runnin’ Utes Basketball Associated Presslast_img read more